[Google Pixel 6 Pro] Gerr1985:
Let me preface here with the following:

I'm on the latest Android 12 beta at the time of this post, and I will lose anywhere from 20-40% of my battery without doing the fixes I'm going to lay out in this post. My phone is an unlocked Pixel 6 pro straight from Google, in use for T-Mobile. I did move from physical SIM to eSIM a while back, which did resolve my Bluetooth or Wi-Fi constant drops somehow.

If you care more about 5G connection than battery, then move along and ignore this, as we'll be putting the phone to preference LTE.

Almost all of these fixes I easily found when googling my issues, save the last step, I don't recall seeing that posted anywhere and tried it on my own to finally get positive results. It ended up fully resolving the stand by drain of my battery.

Here are the settings and steps, followed by some battery results after some use.

Setting 1: Under Dev options, turn off "mobile data always active"

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Setting 2: Under Settings > Network & Internet, turn "Adaptive Connectivity" off. I have not noticed any issues with switching from WiFi to Mobile data, so I'm unsure how much help this setting actually is.

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Setting 3: Under Settings > Network & Internet > SIMs (T-Mobile in my case), change "Preferred Network Type" to "LTE"

It will say 5G recommended, and that should be selected by default.

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Optional, if you want to match me, change or confirm Wi-Fi calling to "Call over Wi-Fi", though I don't think this part matters.

Setting 4 (Final setting, and the part that actually saw the improvement to my battery)

In the same place as setting 3, Under Settings > Network & Internet > Carrier (T-Mobile in my case)

REMOVE the "Automatically Select Network" option, then ensure your carrier is selected under "Choose Network"

* I wondered if this would cause me issue during travel, and during easter weekend, driving 5 hours away to family, it caused me zero problems *

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Within the first few hours, then days, I saw MASSIVE improvements to my battery life vs what it was before with defaults.

Example 1: Throughout my work day I lost only 11%, whereas before I would easily be at 70% or less without hardly picking up the device. I check my phone for alerts, MFA codes, and maybe a few other notifications throughout the day. Not much screen on time. IMHO any new phone should only be losing 0.5-1% with the screen off per hour, and this is the first time this has been the case with my P6P.

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Example 2: Bed at 10pm, awake at 6:23am, and only lost 6%. I'd not thought this possible a week ago...

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And there you have it. I hope this helps someone facing issues with stand-by drain, and I know (like all issues with P6P), this is not affecting everyone it seems. I've been waiting since November for a fix, and this is the best I can get right now. LTE is plenty fast for me, and I'm on my home Gig internet WiFi nearly all the time anyway. I don't know that every single setting in this post is absolutely necessary, but its what is working for me.

I know there have been other posts, but I only saw them as a post of the issue, with an assortment of fixes throughout the threads. I wanted to post this as more of a resolution (well workaround) to an issue many of us know of.

I'll put thread notables after this line (suggestions others have to improve battery life around networking)

This one is from @Morgrain

Both settings can be found under location services. For a further battery life improvement, Google Location Accuracy can also be deactivated, even though I personally let the stay ON, since it makes a difference in GPS location, meaning if you turn it off, GPS becomes noticeably less accurate.