How to install latest client

My first post and a Linux newbie,
I have been running nextcloud v22 server for sometime with a few windows and Android clients.
No major issues.
Long story short, built new computer with random freezing / crashes but no logs and a hard reboot required to get back to my desktop. Uninstalled nextcloud and computer is stable

I have been running Mint mate(20.4) with Nextcloud client 2.6.2-1 build1

Could someone help me install latest client 3.3.1x86-64 that will work with mint - mate to see if this fixes my random lockups. My installed software sources on show client 2.6.2 etc and lower.

Regards Shaun.