@Nathanpgonzalez 

You should be getting faster speeds than that. Here is what I would suggest:

1. Switch Deco mesh to Access Point mode. This will turn off all content filtering and bandwidth management features which might interfere with speed testing. How to set up Deco to work in Access Point mode

2. Turn off all Satellite Deco, leave just Main Deco. This is to ensure you only have one Deco unit running and your phone is connected to it.

3. Keep 2.4 ghz band off in Deco app.

4. Check the associated/link speed on a phone you use for speed testing. This is an old document, but it gives an idea: How to check the associated/link speed on a wireless client

With XE5300 that speed should be at least gigabit.

5. Check in Deco app that phone is, indeed, connected to Deco on 5GHz or 6GHz band.

Try speed testing again. In ideal conditions your speed test results should be close to gigabit. They won't exceed gigabit, because XE5300 has gigabit Ethernet ports and its link to the Internet won't exceed that.

  @Alexandre.  I did the steps. I didnt see a change taking off 2.4 and going to access point mode. i turned back the 2.4 band after ten minutes and didn't see a difference there either.  Any thoughts

  @Nathanpgonzalez 

Verify that your phone is connected to Main Deco: by turning off Satellite Deco and checking Deco app to see that it does report your phone connected to Main Deco.

When done that, please tell the following:

1. What is the associated/link speed on a phone.

2. At what band phone is connected to Main Deco, according to Main Deco.

  @Nathanpgonzalez 

One more thing: what app or web site do you use to run speed test on your phone?

  @Alexandre. Speedtest app by ookla

  @Alexandre. I'm not sure how to get that off the iPhone but I could do it wirelessly off of a computer and it said 2402/1815 Mbps.  I can't do the speed test off the computer tho. But phone was the same, it peaked Higher but it averaged to higher 500s.  I did confirm it was in ap mode and 2.4 ghz band was off.  Satellites were off. Deco app said phone was connected to 5ghz band. 

  @Nathanpgonzalez 

Everything seems to be OK. Your PC connects at WiFi6 speeds. Your Main Deco must have negotiated gigabit wired speed with modem/router - if it were 100Mbps, that would be the max WiFi speed you can see, not 500Mbps.

Yet, something is not right. I am getting more than that on WiFi5 Main Deco M9 Plus, with Pixel 7. The only thing I can suggest is to install WiFi analyzer on your iPhone. It'll give you more detailed info on WiFi connection between iPhone and Deco. I recommend WiFiman from Ubiquiti. No ads and does not overwhelm with too much irrelevant details. You can find it in iPhone app store.

  @Nathanpgonzalez 

One more thing just came to mind. On both iPhone and computer open web site  and note Public IP address it reports. It should be the same IP address when web site is opened on both devices. If it is different - your iPhone might be using VPN.

  @Alexandre. Same IPs. Hey I noticed some similar posts but with different products. I saw your name on some of the replies.  Is this half speed something that is known the happen with to tp link products? Some of those posts are three years old 

  @Nathanpgonzalez 

Those I can recall are for a different issue: you must be running Deco in Access Point mode, use "Test Internet Speed" button in Deco app. That "Test Internet Speed" will report incorrect speed test result. 

Yours is different and does not seem to be common.