Matrix is good in theory but its UI is still confusing. I'm also bitter that my old account that was closed a long time ago cannot be retrieved or reset, which means that I cannot use my phone number again (it's stuck forever to the closed account).
What are you talking about? You do not need phone number. I self host matrix instance and all I did was create username and passwords for people I know and shared with them. They then logged in and changed their passwords. At no point the sign up workflow asked for phone number.
Also, the UI has improved a lot recently. There are number of matrix clients that have appeared on app stores but I still prefer Element which gets regular updates and features.
You don't even need to create usernames/passwords in advance - you can just send your friends custom one-time URLs, which will allow them to enter their own desired usernames and passwords.
I'm sure you can contact the admins of matrix.org and ask for the phone number to be released. (I'm assuming you used that instance, as you mentioned nothing else.) I believe they are reachable at support@matrix.org .
You can provide it for the benefit of your friends (or possibly enemies or attackers) to use it to find your Matrix ID from their pre-existing contact phone number.
