Could I use a monitor with 1.4 hdmi with xbox series s for 1080p 120hz?

for 120hz you need i think hdmi2.1.

besides connecting the s at 120hz is not going to magically let it run at 120fps, you will be lucky to get 40fps on most games. kills my eyes running so slow.

HDMI 2.1 is only needed if you plan to game at 4K for 120hz , on a 4K 144hz monitor, However there's no gaming monitors available at the moment, that yet has HDMI 2.1, the first HDMI 2.1 monitors that are likely to come in are around the same time as the
Series X (Q4) launch or early 2021 (Q1),

1080p and some 1440p monitors can do 120hz over HDMI 1.4 if it's supported, but best ideally is HDMI 2.0 for 1440p for 120hz,

HDMI 2.0 can do 1080p / 1440p at 120hz and 4K at 60hz,

HDMI 2.1 can do 1080p / 1440p / 4K at 120hz.

For the Xbox Series X, it best to get a 4K TV or monitor that supports 120hz and has HDMI 2.1, to get the full potential out of the Series X.

my sons 1080p msi 27" monitor supports freesync and 144hz over hdmi, it also supports 120hz for ps5 and xbox series consoles too. this has hdmi 1.4. Also tested.

Hello Mega! I'm Claus, an Independent Microsoft Community Consultant for Xbox! Glad to be able to help you!

Given that your monitor only has HDMI 1.4 and DisplayPort, and also given that the Xbox Series X only has an HDMI output, your monitor wouldn't support 1440p at 144Hz. HDMI 1.4 only supports up to 1080p/120Hz or 4K/24Hz.

ignore him, you need a monitor that supports the 120hz mode for consoles too, needs to be hdmi 1.4 and above (1.4b for hdr). i use a msi mag artymis 324cp which is a 165hz curved screen 32", it works perfect on xbox one s and the series consoles and series works with 120hz on it with vrr too.

I believe that you need to have a monitor that is Freesync and Freesync has to be supported over HDMI, as well as, the monitor needs to have HDMI 2.0 ports and supports 120/144hz, looking at that, and being G-sync, it seems to have HDMI 1.4 ports which limits
it to 1440p at 60hz

A new monitor is needed if you want 1440p at 120hz,

Pulled this info from a website...

"Nowadays, most of the monitors, TVs, and graphics cards feature at least an HDMI 1.4 port which is enough for 144Hz at 1080p, 75Hz at 1440p, and 30Hz at 4K.

However, keep in mind that some monitors have limited bandwidth over HDMI 1.4 making it max out at 120Hz or even at 60Hz in some cases (mostly G-SYNC and older monitors).

In fact, most 144Hz monitors are limited to 120Hz over HDMI 1.4, but some monitor manufacturers will use custom timing parameters, pixel rates, etc to use the full potential of the HDMI 1.4 bandwidth thus getting 144Hz at 1080p.

So, make sure that the exact monitor you’re looking at supports 144Hz or at least 120Hz over its HDMI 1.4 port – or just look for a 144Hz display with HDMI 2.0.

HDMI 2.0 is also fairly standard and can be used for 240Hz at 1080p, 144Hz at 1440p, and 60Hz at 4K. The latest HDMI 2.1 adds native support for 120Hz at 4K UHD
and 60Hz at 8K."

Here the link to the page..

https://www.displayninja.com/which-cable-do-i-need-for-144hz/