In the first days of public opening LW, I seem to not have had the issues. My progens' first two cubs have text in their bios and I not recall any issue putting it there, and I never use any other device than my Samsung Galaxy Tab S7, which runs on Android, and I use Chrome browser to access petsites.
Shortly after I put the text there, the Bug bit me, though, and now, nothing works. None of the workarounds posted can I replicate.
Today I tried again, to at least put some minor notes on the bios, as formerly due to absolutely wild clicking I had managed to put some (ugly) text in another kid's bio, and I finally decided today is the day to try and replicate THAT at least (minus the ugly), and I succeeded and it's not even difficult, yet, it is definitely not a solution that can be kept forever (also still quite ugly, but at least not messy). It merely is for not-loosing details like maybe re-gening infos or notes on mates, I'd say.
1) open the editor for the info box
2) click the icon to get assistance for putting a link to the bio
(that's the one that looks a bit like a minus sign inside a round bracket)
3) you'll get a pop-up, with two input-spaces: "put text here" and "put link here"
4) write your text someplace else than the bio, like in a chatprogram or in the forums' input box.. - and better keep it short, i'd not trust the these input areas to be designed for big letter counts
5) select that bit of text now, and cut or copy it
6) click and long-hold at the input field, then paste the sentence in
7) copy a default link, like your den overview's URL, or the wolf's own page's URL
8) click and long-hold at the "put link here" input field, then paste the default link to it
9) now, hit the "insert link" button at the bottom of the pop up, so it closes and puts the text to the bio
Note 1 : put the text first! this "workaround" makes use of the fact you can click-and-hold at these input areas to get the "paste" option popping up. if you put the link first, the link's URL will automatically also be used in the text input area, and then you will not be able to erase it, since you are still not able to use the keyboard! if this happens to you, just close the edit box without saving, or reload the wolf's page, so you can start anew.
Note 2: do only use save URLs for the link input area, and also do not make up URLs here! this is, after all, a link that is created in your wolf's bio, and it will lead off-site if someone clicks the text accidentally or on purpose! if the URL you use links to someplace unsafe, which can happen even if you make up the URL, you might be reported and site staff will need to take action! definitely-safe links should be anything you yourself can control and which are from on-site, like the two options i suggested: your den or the wolf you put text to!
Note 3: this method is repeatable. even if the letter count is at a small limit indeed (i did not test this, as i don't need this method for long texts), you can repeat the process and put many links/sentences to the profile one after another. make sure to put signs like "/" or "..." or "-" at the end and/or start of any chunk of text you put on a bio with this method if you want to repeat it, as else the texts will appear at the bio without gaps and words will get meddled together.