The 3G shut down has been discussed on the forums before. A lot of it comes down to many factors including the limited availability of replacement parts for existing 3G equipment.
You can't always believe everything on YouTube, especially when each region on earth is going to have different times that technological standards change. That YouTube video also references articles and websites going as far back as 2017, like at 45 seconds in. It also focuses a lot on the Australian market as that is where the creator is from.
The only thing going anywhere in 2025 is 3G. 3G already shut down in the USA in 2022. Parts of Europe started shutting down 3G as early as 2021, with other countries / carriers shutting it down between then and 2025. Canada was originally going to shut down 3G around the same time as the Americans but delayed it to 2025. I haven't seen any indication that timeframe has changed yet.
No major carriers have announced plans to shut down their 4G networks. 4G isn't going anywhere anytime soon. Estimates are that it'll be around for up to another decade. It's more reliable than 5G is still and it's still quite fast. Some parts of the current 5G network rely on LTE to function.
Apple releases software updates for iPhones, not the cellular carriers. Plus firmware won't change which frequencies the cellular chipset on board physically supports. Any iPhone from the 6 and up has 4G/LTE and VoLTE support on it. The iPhone 6 came out in 2013. Apple no longer provides software updates for devices older than the iPhone X. Android users may have more of an issue due to the huge number of device manufacturers, varied feature sets on the devices, and most Android devices as very out of date since the majority of manufacturers have a very poor track record of providing updates. Especially budget devices and imported ones, and even mainstream devices that are a couple years old.
Most existing devices, like alarm systems, lifelines, and smart infrastructure have already begun the upgrade or replacement process. Most vendors / manufacturers are reasonably proactive. This isn't something controlled by the telecoms.
You will not find a list of devices that will or won't work out there, unless you go and Google the tech specs of every single device manufactured in the last decade. Plus not all devices work in every market.