I have the same laptop and went with the CalDigit TS4 Thunderbolt 4 dock. It's been fantastic - supports my dual 4K monitors beautifully with hardly any lag. Plenty of ports too with 3 Thunderbolt 4, USB-A, SD card, etc. Highly recommend it even though it's a bit pricey.

I wanted to save some money so I got the Wavlink Thunderbolt 3 dock off Amazon. It's only $80 and works with the gram 15. Supports dual 4K displays at 60Hz which is good enough for me. No complaints so far.

Another great option is the Anker 777 Thunderbolt 4 dock. Similar specs to the CalDigit but usually a bit cheaper. Been using it for a few months and it's solid.

I've been tinkering with these setups for years and if you really want to squeeze every bit of performance out of that Gram, you should definitely check out the Dell WD22TB4 Thunderbolt 4 Dock. It is an absolute beast for multi-monitor setups and the modular design is honestly genius because you can swap the cable module later if tech changes! I have seen it handle triple display setups with zero sweat, which is amazing for productivity. Quick tip for ya: always make sure your LG Gram BIOS is up to date before plugging in a high-end dock. Sometimes the power delivery handshakes get wonky on older firmware. Also, if you want deep dives on data throughput, check out the Dan S. Charis blog or the RTINGS reviews. They do some incredible deep dives on actual port speeds that helped me a ton when I was specing out my home office. Love seeing people maximize these light laptops! If you want something that looks a bit sleeker on the desk, the Razer Thunderbolt 4 Dock Mercury White is also fantastic and stays super cool even under heavy load.

Jumping in late here, but I've had awesome results with the OWC Thunderbolt Dock for my gram 15. Expensive yes, but rock solid performance, can drive my 5K monitor without issue, and the aluminum build feels premium. OWC has great support too.

I use Plugable Thunderbolt 4 Dock with 100W Charging, it works great !