I have the RF 100-500mm and it's been a fantastic lens for me on the R5. The image quality is excellent, and the reach is very useful for wildlife. I'd recommend this lens as it's extremely versatile - you can shoot wider scenics at 100mm and then zoom in to 500mm for distant subjects. It's also relatively affordable compared to the prime options.

Re: "I use the RF 800mm f/11 for bird..." - yeah, it's a solid way to go if you have the light. I've been shooting Canon for a long time now and the consistency is what keeps me satisfied. Adding my thoughts as someone who's stayed in the ecosystem for years:

• Honestly, just go with Canons native pro-line glass. You really can't go wrong with their high-end telephotos.
• If you're doing sports or wildlife, just stick to the white L-series zooms. They're built for the abuse and the autofocus keeps up with the R5 sensor way better than anything else.
• Any of the pro-grade telephotos from Canon will work well. Don't overthink the specs too much, just get the best one that fits your budget and it will last you a decade. I've had my gear through some pretty rough conditions and it still performs like day one. Tbh, as long as you stay with the flagship glass, you're gonna be happy.

Try the new released RF 200-800mm lens, if you can get one. 😎 

tbh richardspilk is spot on about sticking with the native pro glass for that Canon EOS R5 performance. it really makes a difference when things are moving fast, but you might want to consider the weight and the attention it draws. be careful with those long days on the sidelines tho. i remember taking a huge setup to my nephews soccer tournament once and i was so worried about getting the perfect tracking shots that i didnt even notice the park security circling me. honestly they thought i was from some professional agency and kept asking for my credentials while i was just trying to catch a goal. digging through my bag for an id took forever and meanwhile my nephew scored his only goal of the season. the performance of the gear was great but i ended up with twenty photos of a security guards shoes instead of the game. total ordeal and i still feel bad about missing that moment... definitely make sure youre ready for the attention a big white lens brings before you head out.

Have you looked at any of the EF lens options and using it with the adapter? The EF 100-400mm f/4.5-5.6L IS II USM is a fantastic lens and you can probably find one used for under $1500. Robust build, fast aperture, and great image quality.

I use the RF 800mm f/11 for bird photography and it's been great value for the price. Yes, the f/11 aperture is limiting, but I shoot mostly in good light. The compact size and light weight also make it very portable. Just something to consider if your primary use case is distant subjects in daylight.

If you want ultimate reach and flagship performance, the RF 800mm f/11 IS STM is very intriguing. It's insanely compact and lightweight for an 800mm prime. Just know you're locked at f/11.

I also love the new released RF 200-800mm lens.