I can help you out. I'm a Dolby certified colorist for television and web. Davinci Resolve is a good choice for your HDR work. I know I addressed this in some posts about a year ago, but here's a quick synopsis. First of all almost all video acquisition can be turned into HDR, but for stunning video, shoot In D-Log or HLG. Most productions are finished in Rec 709, but this means using a LUT and basically throwing away most of your extended color and dynamic range at the beginning of the process. Starting in Resolve, set your general settings with HDR metadata ticked and make sure you are working in a good colour depth, probably 10 bit for what you are doing. Dolbyvision can work in 12 bit, but this is overkill for Youtube and Instagram. Also Dolbyvision doesn't work on Youtube, but does work on Vimeo. You are better off using HDR 10+ for Youtube.
In your color tab I would work in Davinci wide gamut. This is a huge colour gamut and will also interpret your incoming footage correctly for say D-Log without any LUTs. Remember LUTS throw all the good data away so do not use. In Davinci wide gamut, you can select clips, right click and look at how the incoming color and gamma is being interpreted on a clip by clip basis. If there is any issue, you can select the correct color and gamma for each clip.
I'll include a couple of screen grabs for the color page under project settings at the end. To set up DWGamut, go to the top of the page and select Davinci color managed. Then under color processing mode go to custom. At this point select Davinci Wide Gamut RGB. This will be your intermediate color space, much larger color world than any camera data you will bring in. Your output color will be Rec 2020 and either HLG or ST 2084 as gamma for Youtube. Again I show this in a screen grab. I use ST 2084, which is a universal standard for gamma curve for HDR and is the magic sauce that extends the highlight data far beyond what Rec 709 can provide. Set your scopes to HDR. By the way, here are the specs for HDR on Youtube:
Upload High Dynamic Range (HDR) videos - YouTube Help
In the color room of Resolve set your video scopes in the HDR mode. Again, I'll add a screen grab to find the three little dots to select this. Select HDR as your scope style. You will now have levels available to 1000 nits. This is the current standard and in the future may go as high as 4000 or 10,000 nit, the theoretical limit, as technology catches up. Suffice to say that 1000 nit is adequate for current HDR work and you'll want to keep your highlights without clipping at 1000 nit or below. Rec 709 is only 100 nit, just so you know, so HDR stretches your highlights significantly, but these values are a log scale so not 10 times brighter.
Hopefully you are able to view your results on an HDR screen. If you are using a MacBookPro, go to settings/displays and set your monitor for HDR ST2084 so your screen will display HDR. I use a professional 32 inch Flanders HDR grading monitor, so I have the luxury of watching on a large in screen in HDR, but many laptops have excellent displays, especially the MacBookPros. (Sorry for the vertical resolution in my examples, but this was and HDR video I did for New Years for Instagram)
Once you have finished your color grading select the color menu and drag down to HDR 10+ and select analyze all. Sorry the words are greyed out here, but this was processed with DolbyVision so it doesn't recognize the HDR 10 menu selection. I have a big yellow arrow so you can see the greyed out words. This will set all the metadata for each shot for when you export. This metadata will tell your playback devices on Youtube how to display your production. If your metadata doesn't get embedded, your production may not process to HDR on Youtube.
After this go to the deliver room and create and H265 movie. By default this will use the colour science you've previously set up so you don't need to change anything. For DoblyVision you have to select the 8.4 standard, but this is for HDR 10+ so I wouldn't change anything. You will want to tick embed metadata so the metadata is part of your movie. This does not get selected by default in Resolve. I usually use multi-pass encoding and turn off optimize for speed if it is selected by default. I've found this can cause some artifacts in the video.
Add your production to the render queue and render out. Upoad to Youtube and wait. Depending on the length and resolution it could take hours. I don't know why Youtube is so slow to generate the HDR results. Vimeo is very fast, in comparison. Don't give up hope and keep checking back. I think I've covered most of it. I'll try adding some screen grabs to this and then let me know how you make out.
Hopefully this is enough to get you going. Send me a message if you need more help. Cheers!
