When it comes to the LP-E6 series batteries like your camera uses, I've stuck with Canon's OEM (and have a dozen of them, shared between 3 cameras).
That said, some brands such as "Watson" are probably fine. "Wasabi" might be fine, too. I've heard of them but haven't used them so can't say from experience. Another brand I've heard good things about but haven't ever used is "Jupio".
In particular, I don't trust any battery that comes with it's own charger. Look closely at it to see if there's a warning about using any other (such as Canon) charger... or vice versa, to not use the charger with any other battery (such as Canon OEM). These "Neewer" batteries are an example with such a warning:
https://www.bhphotovideo.com/c/product/1733137-REG/neewer_66600396_2_2250_mah_lp_e6nh.htmlp. The same warning is on these "Green Extreme" batteries:
https://www.adorama.com/gxlpe6nhk1.html. To me this suggests some possible compatibility issues. Maybe that's the case, maybe it's not. I'm just not willing to take the risk to save a few $.
These modern battery like the LP-E6NH have chips inside and firmware. With older types of batteries such as Canon BP-511 and BP-512 I had no concerns about using 3rd party and did so a lot. But I'm more careful with the more modern batteries.
Also notice that there really isn't that much savings, if any, buying the "quality" 3rd party LP-E6NH:
https://www.bhphotovideo.com/c/search?q=lp-e6%20canon&filters=fct_battery-series_3189%3Acanon-lp-e6nhCanon LP-E6NH...... $79
Watson LP-E6NH..... $59 ($20 savings)
Jupio LP-E6NH........ $85 (more expensive?)
Manfrotto LP-E6NH.. $60 ($19 savings)
Also check the 3rd party battery's power rating. In some cases I noticed they had less than the 2250 mAh of the Canon. This might make for slower frame rates or other performance compromises.
On their website, Wasabi don't have a charger warning, claim they match the power of the Canon battery and state that they are compatible with most Canon cameras that use the LP-E6NH. But they don't yet list the new R6 Mark II, so I would guess they haven't tested it yet. Might be worth asking them, as it would be a good deal at $28 apiece or two batteries for $45.
https://www.wasabipower.com/collections/canon-lp-e6/products/canon-lp-e6nh-battery-by-wasabi-power?variant=42061560414435When it comes to the LP-E6 series batteries like y... (