core runs on an rpi. knots does not.
therefore, running knots is not the solution, it is the problem
it's been a long time since i did an ibd, but i'll think about testing low memory configs. are you running something like start9 or umbrel? and how did you install bitcoin? 
I run Knots on an old laptop. I also run core on another (relatively new, low end laptop) for my BTCPay server. Both machines are with 8 gigs of RAM, and both took around 4-5 days to fully sync. Haven’t tried on a rpi, but a couple of people I’ve talked about trying to do a fresh IBD at 4 gigs told me it took them more than 10 days to finish over a decent internet connection.
🤔 these are manual installs on linux?
The Core one is. The Knots one I run on Windows, since I feel more comfortable with it. But this wasn’t an option for the BTCpay server, so I went with Core, since it’s easier to setup (more manuals available).
is it one of these deployment options? what core version / Linux distro? https://docs.btcpayserver.org/Deployment/
Core: We're going to enforce fundamental changes that noone asked for and with minimal user benefit while ignoring the likelihood of unknowable consequences.
ynniv: Knots is clearly the problem here.
the changes aren't fundamental, and the user benefit is a healthier bitcoin. we can infer the consequences by using the grey matter between our ears, or at least between my ears.
no one ever asks for less complexity, and you're welcome to run whatever floats your boat
