Upgrade from 7.1.10 to 8.1

[DarkCorner]

I have an old server with Proxmox VE version 7.1.10 that I haven't used for a long time. I would like to update it to the latest version, but I find instructions to upgrade from 7.4.
It is subscription-free because it was only used for personal testing and will still be used.
I don't want to do a new installation because there are disks already configured and I can't change their configuration now.

 

[lolhunter]

You need to apt update && apt upgrade to get 7.4 from 7.1.1 and then upgrade from 7.4 to 8.1

 

[DarkCorner]

I already did this, but I get this error:

Some packages could not be installed.
This may mean that you have requested an impossible situation or
if you are using the unstable distribution that some required
packages have not yet been created or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:  pve-firmware : Conflicts: firmware-linux-free but 20200122-1 is to be installed

Reading in the forum I find that the solution is to remove pve, but does this mean losing all the content such as disk and VM configuration?