The Kodi setting for Limited doesn't do what you think it does I'm afraid. It's been confusing for years.
The Kodi tick box for Limited Range option is only useful when your OS is using Full range output (and would map black to 0 and white to 255) but you want to force Limited Range output (with black at 16 and white at 235) because you're feeding a display that won't accept Full range output (or you want to preserve <16 and >235 content and/or avoid the banding that rescaling can cause). This was a useful thing with some Intel GPUs a long time ago...
HDMI InfoFrames these days mean this is less useful than it might seem (as InfoFrames are now routinely used to flag Full or Limited range from source to display). If your OS is already set-up for Limited output then you get grey blacks and dim whites if you also tick the Limited option within Kodi, as you will if your TV is in Full range mode or your OS is in full range mode and TV automatically detects this nd you select Limited in Kodi.
For a Raspberry Pi, in my experience with Sony and LG TVs, you should leave the Kodi settings on default and your TV Full/Limited range settings on Automatic if you can (so InfoFrames are followed correctlu) If not I'd use Limited (as my TV HDMI setting) as my starting point - as that's the near-universal standard for HDMI video devices.
I've never had to alter my Kodi settings or TV settings on a Pi 3/4/5 running LibreElec to get correct black and white levels. Most HDMI systems default to 'Limited' or 'Video/Broadcast' levels (16-235/64-940) as that is what broadcast video production and distribution uses (other than Dolby Vision ICtCp stuff). If you remap Video/Limited to Full you can clip <16 Blacker-than-Black (not usually an issue - though it makes PLUGE tricky to use) and >235 Whiter-than-white (more of an issue as 100-109% are valid video levels - particularly in broadcast TV use)
From your posts above
TV: Limited
Kodi: Full (which doesn't actually mean the Pi 5 is using Full range - it just means Kodi isn't compensating for a Full range output to a Limited display...)
Gui looks the most natural... deepest blue colors from Estuary. HDR content is dark, normal content is normal.
If the Pi5 is correctly configured for Limited output automatically at an OS level (which happens pretty much all the time on a modern HDMI-connected display) - you shouldn't need to select Limited in Kodi's settings.
Is what I would expect to be normal. When you say HDR is dark are you objectively comparing it with the same UHD HDR content via a different player route (i.e. comparing a UHD HDR BD player output vs Kod playing a UHD BD rip of the same disc on the same display) or just making a subjective comment (or worse comparing with an HD SDR version of the same content).
It's normal for HDR versions of movies to appear darker in PQ (i.e. HDR10) HDR than the same movie release in HD SDR (say comparing a UHD HDR BD with an HD SDR BD) because HDR PQ10 is based on SDR content brightness being at 100nits max (with HDR highlights etc. going >100 nits), whereas most people watch SDR content at display settings brighter than this (so the SDR content often hits 200 nits or more), and thus when PQ content keeps the SDR range of an HDR signal at 100nits 'it looks dark' is often the comment you hear (as people are watching SDR content pushed into the HDR range of their displays - as 100 nits is quite dark for normal viewing conditions).
I guess I'm asking whether you are saying for certain that HDR content is definitely incorrectly replayed - or you just feel it's too dark?
***EDIT - It may be best to leave your TV on Automatic rather than fixing it at Full or Limited - as regular SDR content is almost always 16-235/64-940 video/limited levels - as is HLG HDR (as used by services like BBC iPlayer). However PQ/ST.2084/HDR10 stuff may be using 1-1023/1-254 full range instead and flagging accordingly using HDMI Infoframes ***
