I am having the same issue in dark theme on the iOS (iPhone and iPad) version. I copy/pasted a bunch of entries from my old journal in the Pages app on macOS, which were black text on white background, into the macOS version of Diarium.
On macOS in light or dark theme, the entries look fine.
On iOS (both iPhone and iPad) the entries look ok in light theme, but in dark theme they are very dark font on dark background, making the entries unreadable. Of course if I make a new entry by directly typing it (not copy/paste from Pagers or other source), it works fine as expected in light/dark themes.
I am a new user of Diarium and have the Pro versions of both iOS and macOS. I really like the app a a lot! I had been using a simple text file with entries going back to 1987 and recently imported that text into Pages on macOS. I decided it was time to use a proper journaling app that had more modern features such as secure sync via iCloud. Diarium is it!! Now if I could just read all my meticulously copy/pasted entries from 1987 to present it would be wonderful 🙂
I believe simple adding the ability to set font color in the entries would be all that is necessary - or perhaps when accepting pasted a text, strip off any formatting to import just the raw text and let Diarium deal with font/background color in light dark theme.
Thank you for a wonderful and very functional app!
iOS/iPadOS 16.1 and macOS 13.1 Ventura.
Diarium iOS: 2.9.37, macOS 2.9.37