This actually should work. You just need to copy the content of the pem file to the private part of the key when copying it into Termius app in the Keychain section.
We’ll double-check it.
If you have any other problems please contact us here – http://support.termius.com/
ThanksCharly Arg supported this idea ·Charly Arg commented
I can confirm that I converted my .ppk from putty to .pem using puttygen, and then I opened the .pem file with Textedit, copied and pasted over the private key in the keychain in Termius and it worked perfectly!