Used both these, one south and one east of Pollenca:
http://www.tramuntanatours.com/mtb.html
Great variety of routes when I last went, guide was bonkers fast and more capable than me (not hard) so could have slowed down a bit!
https://www.roxybikemallorca.com/mountain-bike-events-coaching-english/index.php/
Great routes again, mix of XC and DH, the XC bits can be quite quick as there is lots of german lycra action in the area, the DH is great around Son Servera but its not Tramuntana length downhills
Have followed this guide book around the Arta area quite a bit (our place is on this side!) in the Parc natural:
https://www.rockandride-mallorca.com/fantastic-mtb-trails-mallorca/
Follow these guys on insta and love their gravel routes as this is really a wonderful part of the island for that, if I’d been able to make it our there recently it was on my list to do:
https://www.amigobikes.com https://www.instagram.com/amigobikescalaratjada/
They’ve even had a world mtb champ out with them!
Hope that give a bit of food for thought