Jisho

I'm not sure I would describe it as merely "outdated." It's the classical orthography.

I don't think the JMdict project adds classical orthography to every entry. For instance, the listing for 氷 does not list こほり, the entry for 言う does not list いふ, etc.

Yep, that's called 歴史的仮名遣い

It's often listed in dictionaries and definitely good/important to know if diving into older texts. But yeah that would have to be added to almost every entry then in JMdict, not just a single word. (たまへ is btw not really a "dictionary form", that would be たまふ or たまう, it's already a deflected form, either 已然形 or 命令形)

If you need the classical spelling for anything, you're probably at a level where you're comfortable using an actual 古語辞典 anyway