SSDs actually do not require TRIM to work, they just slow down after they run out of free blocks. I still have in use a bunch of old SLC SSDs that do not support TRIM, and while they had a manual TRIM utility for XP, no modern SSD will have such a thing available.
Fortunately what works just as well is using any free-space zeroing utility when you notice things starting to slow down. In Windows I like to use sdelete -z C: /accepteula or cipher /w:C or in Linux there's sfill -llz (one of the secure-delete tools)
The last Intel chipsets to not support TRIM were for Pentium 4. I can verify that TRIM works just fine on the very oldest Southbridge intended for Core 2 which was ICH7, even though that chipset does not even support AHCI.
I used a linux command which can pull the sata information and it was 1.5 and 3.0 speeds. As for the windows fourm post one reply stated that IC7H would not work with a SSD. I did buy a 240 HP which is 3.0 sata. Now I got to find the time to install the SSD.
I have two of those boards. They are G31/ICH7 and TRIM does work on those, at least in Windows (Win 7 and Win 10 defragmenter allows you to optimize the SSD drives instead of listing "optimization not available").
Note if the BIOS is set for "Compatible" then Device Manager only installs a 100MB/s UDMA5 controller, while "Enhanced" installs the Standard SATA Controller because there's no AHCI, but it presumably works at SATA-300 regardless (only ICH7-M for laptops was SATA-150 to save power). This is also one of the last Intel chipsets to natively support IDE, so if you have the IDE header and either a spare IDE drive or compactflash card you could use that with no jmicron driver nonsense.
I have not had a IDE drive in many years though My vary first DIY build was such a system 1994 its currently still kicking running win XP sp3 at my friends home in Indiana. His daughter still plays CD games on it. though no internet access now days. It is a Pentium 4, 3.0 the good old beige case. If it died I am postive I would get a text about it.
I installed the SSD and trim was active on the system. I installed Linux mint mate 20.3. Confirmed Trim was active. I read article and I need to find it which was about Adding SSD to older systems and the benchmarks.