Why would Bluewallet create anything when I only imported a watch only xpub? I tried signing txs that were done with with 0', 44', 84' with the same imported xpub with Sparrow but Coldcard refuses to sign the psbt.
This is what Bluewallet, which still has its default 44' path, produces:L and it gives no obvious option to change the path:
https://i.nostrimg.com/1533181614e1c85351ff568fa070124f0af26ffc4720f319a2d79adbd4e89c3a/file.jpg
https://i.nostrimg.com/c681d38c97e3cbc0de1da00dd086109dc30765f1afb28d483c795559c9a4b24f/file.png
I've been where you are. The problem is old versions of Blue wallet would always create legacy wallet if a xpub were imported even if derivation were 84. If I were you I would put your coldcard aside and use your mnemonic, load it in a hot electrum with this "weird" setup: legacy with 84 derivation. Your funds will be there ready to be transferred.
I think it is the ONLY way as far as I can tell from researching the issue. It is the most up to date version of Bluewallet though.