Cannot edit trusted domains (Process Control Extension required)

Hello again, friends on the internet!

Unfortunately, I still haven’t been able to fully set up my Nextcloud Box. I am currently running Ubuntu Core with the Nextcloud Snap. When I try to edit the trusted domains it says that I need the Process Control (PCNTL) extension. I cannot install it manually, however. Following the official guide on installing it fails, I cannot use wget because it isn’t supported in Ubuntu Snappy Core. I found that there are work-arounds for that but I’m not sure if maybe I did something wrong previously. How should I progress from here?

Thanks in advance for your help!