How to Interpret Lomb Scargle periodogram
The x-axis of a periodogram is usually a frequency, measured in inverse time units. It is possible to plot the inverse of frequency, in which case the axis would be non-linear.
In your case, the x-axis looks linear, and the the code you present appears to be using something labelled as a frequency on the x-axis. Therefore I would assume (though I would read the documentation for the functions you are using) that the x-axis is frequency. The units will be based on whatever units are in your input. i.e. It is just the inverse of whatever you are giving it for the times - in this case, $d^{-1}$.
If your sampling rate is once per day, then you are getting no reliable information at all about frequencies $&gt;1$ d$^{-1}$. The stuff you should be concentrating on lies between $0\leq f &lt; 1$ d$^{-1}$. Even in this range you won't have good fidelity on signals with $0.5&lt;f&lt;1$ d$^{-1}$ because they are undersampled. You can also expect to get aliasing signals in the range $0\leq f &lt;1$ that are caused by true signals (including those with higher frequencies) aliasing with the 1 d$^{-1}$ frequency of your sampling.
It looks to me, by eye, like you might have a genuine signal at $1/7$ d$^{-1}$, corresponding to a weekly variation. There may be a weaker signal at much lower frequencies that might correspond to a monthly signal. The 2 signals either side of 1 day look like aliases of the weekly signal with the sampling frequency.
I would highly recommend reading VanderPlas 2018 for a thorough discussion of the Lomb-Scargle periodogram and its interpretation.