Minecraft Realms :client outdated

I played Minecraft earlier today in Realms.  Now I get:

"Your client is outdated and not compatible with Realms.

Please update to the most recent version of Minecraft".

I'm on Linux Mint 20 Ulyana.

There's a launcher update available: I click here and go to that page and select the Debian update and install it.    I get "There was an error launching the application".

If this is about JDK version () you need to make this easier or more transparent.

I appear to have default-jre 2:1.11-72.

Denial Of Service, guys.