Rokwiia
WKR
Personally, I prefer barometric watches for altitude and have for 24 years. Garmin has a caveat on their website about relying on GPS for altitude:
https://support.garmin.com/en-GB/?faq=QPc5x3ZFUv1QyoxITW2vZ6&searchType=noProduct
https://support.garmin.com/en-GB/?faq=QPc5x3ZFUv1QyoxITW2vZ6&searchType=noProduct