I have a 2018 Pi-Top v2, equipped with a RPi3. Would it be possible and practical to upgrade it to an RPi5? Is there maybe a guide on doing this somewhere?
Are you refering to the Pi-top CEED or the pi-top laptop version 2 which is the pi-top[3]?
The product I bought was described as “Pi-Top2 Educationsnotebook mit Raspberry 3+ 14” Display, US-Layout, Inkl.Inventors Kit" (in Switzerland.) It’s definitely a laptop though.
Yes. That’s it. Mine also has the speakers and a breakout board.
I see it is, look in the pi-top[3] forum. RPi 4 has some problems due to repositioned USB and Ethernet. Rpi5 has them the same way as the RPi3. Power may be your problem, it will complain that the power supply isn’t compatible, albeit if the “Hub” power capability the same as the Pi-top[1]/Ceed can supply 3.5A max. And the cooling will need to be sorted due to the weird Connector from the Hub to the RPi. Hope that helps?
Thanks for the advice.
Regarding the power supply, do you think the official Raspberry Pi 27W USB-C power supply would be able to handle the pi-top[3] upgraded to RPi5?
Cooling is another problem.
I have a pi-top[1] running with a RPi5 and it runs fine. You need the 18V i/p for the Hub, battery and display. You may need to upgrade the 18V pwr supply that to give you a few more Amps. Magic thing is that there is (On my Hub anyway) a 18V supply available to use, which is available on the proto breakout board. Whilst the RPi5 works with a warning with the standard 3.5A supply I was going to see if one of the chinese Buck converters that handle the PDR3.1 protocol that the RPi5 needs. In any event it should be possible to get > 3.5A using a buck converter and you can tell the OS to ignore the fact that you don’t have a PDR power supply. I don’t think that giving it 5V rather than 5.1V will be a problem , hasn’t been for me.
Wait to you try and get the latest operating system working 
Just realised the HDMI connectors will be a problem. Someone suggested a waveshare product for the CM4, https://www.waveshare.com/CM4-to-Pi3-Adapter-B.htm. It would be a neat solution, doubt they will do it for a CM5 tho, and cooling problems in spades. lots of ideas here The pi-top [3] + Raspberry Pi 4 (Franken [3])
Thanks for the further advice.
Could pi-topOS be a problem on the RPi5? The webpage only mentions support for RPi3 & 4. Is there any reason to want to use pi-topOS rather than, say, standard Raspberry Pi OS? Will the mousepad, keyboard, screen, etc. still work OK?
pitop OS, I think I had it working, but standard bookworm needs some software loading to get battey monitoring and Power switch working. Problem is for the piTop[1] and CEED power switch doesn’t work, and you lose the Battery ICON… Pi-Top are not really interested in supporting these old HUBS, which is a shame. I’d try the pi-top os 1st and see how you get on (the approved version is 32bit) https://knowledgebase.pi-top.com/knowledge/pi-topos-64-bit
As another thought, but I haven’t tried it, you may be able to connect,using a standard ribbon cable, the GPIO from the proto board pins to the RPi5, then just move the hub top the left and get some short cables to connect everything up. You will need a 5V USB C connection from the proto board to the RPi5, and you may need to snip the 5V cables on the Ribbon cable. (The GPIO pins that the Hub need may well be connected to the GPIO header on the Proto board, but qui sait…) Just a thought