The biggest issue with Matter is a universal app to control everything. If you do a Google search for "Matter, The Great Universal Smart Home Standard, Is Already Fragmented" there is a good article about how it's already a mess, at least in version 1.0. It points out how they are still leaving how matter is implemented up to the manufacturer which means you still need multiple hubs and multiple apps. Below is a copy/paste from that article.
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Philips Hue: Philips Hue will not allow any form of multi-admin control at all. You’ll have to control Philips Hue (and only Philips Hue) devices in the Hue app.
Update: Since publishing this article, a Philips Hue PR rep reached out to clarify that Hue Devices will be open for control in other apps. Other devices can not be controlled in the Hue app. That’s a shame, as the Hue app is easily one of the best smart home apps available. But still an improvement over what we were originally told.
WiZ: WiZ, which shares the same parent company as Philips Hue, will also allow its devices to be controlled by other apps. But it won’t update its app to control other devices.
Nanoleaf: Nanoleaf will also allow its devices to be controlled by other apps, but it’s unclear if you’ll get to control other devices in the Nanoleaf app.
Aqara: Aqara will allow both control of its devices through other apps, and controlling other devices through its apps. However, you’ll need an updated hub, and the current one isn’t Thread capable. Aqara plans to release an updated multi-protocol hub later.
Eve: Eve is, simply put, the gold standard of Matter. The company will update its app to control other Matter devices and allow its existing devices to work in other Matter-compatible apps. Eve is far ahead of nearly every company, having long supported the Thread protocol. (Eve currently doesn't have an Android app though, only iOS but they are working on an Android app).
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Hopefully the above will change but as a HA user, I don't care as the latest release of Home Assistant added Matter support and Home Assistant can now be a Thread border router. You can get a Home Assistant SkyConnect, which is a 30 dollar USB dongle that is ZigBee 3.0 and will get an update to support Matter. It's plug and play. The only issue is Nabu Casa has just recently started selling hardware and they can't keep up with the demand. Right now I have a 30 dollar Deconz USB ZigBee 3.0 adapter. I can do firmware updates to most but not all ZigBee devices (Hue is about the only one that doesn't allow it) with Zigbee2MQTT.
It controls Hue lights, Aqara devices, and pretty much any ZigBee, Bluetooth, Wifi, Z wave devices, and is an Android ADB network controller for my Sony Android TV so I can either tell Alexa or Google to "turn on Sony Netflix" and have Netflix instantly open on my Sony TV.. All in one app and being able to use the same trigger words for Google Assistant and Alexa. All local outside the webhooks for voice control as it pushes everything to Google and Amazon automatically if you allow it to.. They currently support over 2000 integrations, everything from lights up to cars. Nabu Casa also acquired ESPHome which allows you to flash devices over Wifi with a browse like Wifi lights. Their UI interface has come a long way, especially for scripts and automations. You used to have to know YAML but that's changed a lot. In fact, Google has shown off an advanced automation/routine utility and it uses YAML and it is 100 percent a rip off of HA. It's in beta but if you looked at it compared to HA, the YAML is 100 percent the same. It's also all documented by HA/Nabu Casa very well and has a huge user support base if you are just starting out
HA used to require some technical knowledge but that's changed a lot. I recently purchased a Aqara P1 motion sensor. Home Assistant saw it as soon as I yanked the plastic between the battery and the connector. Within 15 minutes I had it set up in my mailbox and created an automation to send me a text message anytime the mail is delivered with the date and time in the text message. Or at least everytime the mailbox is open. It can track energy usage from smart switches and solar panels and track smartphones (if you want). All through the GUI utilities built into Home Assistant, no YAML needed anymore except for very complex automations.
While not personally an Apple user you can set it up as a HomeKit Controller. It just emulates it so you can have Android and Apple devices all work in the same app. Not sure about Siri but not an Apple user so haven't looked into that personally. To me, HA is the glue that fixed the issue Matter is trying to solve while Matter is leaving some things up to manufacturers to pick and choose what you can control with their apps and hubs. Considering a Hue hub is like 50 bucks, having a raspberry pi 4 and ZigBee USB adapter do all that for 60 to 70.bucks is a no brainer to me.
The thing that's always confused me is ZigBee is just a protocol like Wifi yet everyone makes you buy seperate hubs Why? Well money of course but imagine if you had to buy different wifi routers with say, a D-Link router only working with D-Link WiFi devices while needing a Asus router to get WiFi with devices with an Asus wifi adapters. That's just an analogy but that's the way I've always thought of it. While Matter is trying to solve that issue it's already solved to me personally. With HA you can control almost any ZigBee devices with one adapter that's cheaper then most of not all ZigBee hubs by Hue, Aqara, and others.