30 minutes ago, xentropa said:
It is also worth noting there are different versions of HDMI with different transfer rates and video specifications although they all use the same physical cable. I don't know if ur problems are resulting from an incompatibility.
HDMI ports have versions. HDMI cables have different "types". They use the same physical port, but you will be limited by the lowest port version or cable type, whichever is worse. From Wikipedia:
As of the HDMI 1.4 specification, the following cable types are defined for HDMI in general:
- Standard HDMI Cable – up to 1080i and 720p
- Standard HDMI Cable with Ethernet
- Standard Automotive HDMI Cable
- High Speed HDMI Cable – 1080p, 4K 30 Hz, 3D and deep color
- High Speed HDMI Cable with Ethernet
A new certification program was introduced in October 2015 to certify that cables work at the 18 Gbit/s maximum bandwidth of the HDMI 2.0 specification. In addition to expanding the set of cable testing requirements, the certification program introduces an EMI test to ensure cables minimize interference with wireless signals. These cables are marked with an anti-counterfeiting authentication label and are defined as:
- Premium High Speed HDMI Cable
- Premium High Speed HDMI Cable with Ethernet
In conjunction with the HDMI 2.1 specification, a third category of cable was announced on January 4, 2017, called "48G". Also known as Category 3 HDMI or "Ultra High Speed" HDMI, the cable is designed to support the 48 Gbit/s bandwidth of HDMI 2.1, supporting 4K, 5K, 8K and 10K at 120 Hz. The cable is backwards compatible with the earlier HDMI devices, using existing HDMI type A, C and D connectors, and includes HDMI Ethernet.
- Ultra High Speed HDMI Cable (48G Cable) – 4K, 5K, 8K and 10K at 120 Hz
So if the cable is very old/bad quality, it might simply not be enough for 4K. OP doesn't mention what resolution the Dell monitor is, so it could be working fine at 1080p, but is lacking for 4K (especially if it a newer LG TV, which supports 120Hz).