So me and my friend wanted to play 1.18.1 (Since we had been playing a lot of older mods on 1.16.5 and wanted to give 1.18.1 a go) But It seems he couldn't open his 1.18.1 (or anything newer than 1.16.5) we migrated his account into a Microsoft account but now he isn't even able to go on the launcher's home screen. He was just stuck on the login page, and when he tried to login it said he was offline? Yet he clearly was online since he was calling me at the time. Any help? If its important he was on a Linux Ubuntu. (Debian I think)
First things first. If you can, use the generic launcher and not the launcher for your distro, because the generic launcher can be installed in your home and you have full control of it if something goes wrong. Unless you have some linux administrator skill.
Second, for 1.18 onwards you don't need to have Java preinstalled anymore as the launcher will download its own jvm from Microsoft, and it's a JVM optimized for Minecraft (I mean the configuration, not the code).
Finally, check your egress (outbound) firewall rules, since the launcher have to do a bunch of downloads from different providers, so you have to allow almost any http and https traffic.