If anyone has a similar issue with USDT stuck or lost because of sending it to a BTC wallet i would definitely recommend sending him a message.
Thanks thomasxyc for your kind words.
It's been a pleasure chatting with you and guiding you through the steps.
I'm glad we figured it all out !
Next time you should be careful when sending, especially if the wallet was a platform or a closed source wallet.
Well, in this case it was an uncommon derivation method that was used by the BRD wallet.
The settings were in the "BIP32 tab",
"Client" : "MultiBit HD",
and "BIP32 derivation path" : "m/0'/0"
This is why Thomas' public address was not showing on the default page.
I believe this to be specific to this user's case and not a generic solution for everyone facing a similar issue.
I have also helped someone else who got mistakenly their USDT sent on the Binance Smart Chain as a BEP-20 Token.
With all these tokens, sidechains, tokens on sidechains, this is getting confusing.
Anyway, if someone is stuck in a similar situation, do not hesitate to send me a PM.
I will never ask for your seed or your private key.
(If someone does, this is not me but likely an impersonator.)