Heh, your comment actually made me finally go and resolve a problem I've had since I got this laptop in 2020. I didn't have SVM virtualisation acceleration enabled because that made Windows unable to boot somehow. A bit of twiddling after, it finally did! VirtualBox runs! Docker runs!
...but why would I use Docker for something like this. Might as well blow the dust off of my FreeBSD virtual machine and run Forgejo there!