I have two Microsoft accounts, Account A for my Windows 10 system and Account B is exclusively for my alternate Legacy Mojang account. I do NOT want to merge these accounts. The Minecraft <Java Edition> Launcher becomes confused at this and seems to default to the system account and freezes up before spitting out the following error;

Minecraft Launcher is currently not available in your account. Make sure you are signed in to the Store and try again. Here's the error code, in case you need it: 0x803F8001

I will NOT play <Bedrock Edition>.

I will NOT migrate my original Legacy Mojang account.

I wish to play the game I paid good money for, even if it's offline only.