100PCS UR K3 Waterproof Wire Connectors, Gel-Filled Telephone Cable Splice Terminals, Clear Butt Connector for Network Data Line Junction

If you want more room inside, consider using a structured medial box, like https://www.amazon.com/Leviton-49605-140-Wireless-Structured-Center/dp/B07V4TBNZQ/ Could mount it flush in the wall where that cluster of Cat wires are coming out. Then you can terminate everything data to a mini patch panel, voice to a phone d-block, and fit the CATV splitter inside without squishing and overly twisting everything to make it all fit. For splicing Telco wiring, I use UR connectors like https://www.amazon.com/ZCLGOOD-Waterproof-Connectors-Gel-Filled-Telephone/dp/B0FKNR657P/ But I'm also only joining 2 or 3 wires, so a phone d-block might be better with as many as you have spliced together, something like https://www.amazon.com/dp/B00A4MLJH2/ Other configurations of these exist, just giving you examples to work from.