If I have a home server connected to Proton Drive for example, would that be sufficient to back up my data?
Acceptable for what? What do you, personally, consider an acceptable amount of loss, and time and money spent on recovery?
I don’t have any life-or-death critical data, so I have one local backup in case I corrupt my server again. If my house has a fire or flood, or lightning strikes and fries everything, or my stuff gets stolen, that loss is acceptable to me.