Are we sure that there is no truth? Of course it's fair game to say that what I'm saying isn't really the truth as there are a few subjective premises behind what I believe in but surely there are some truths that can be derived from life? Like how 2+3=5 or I am inside a room in a house when I was typing this message out. Is it fair to say that there are no truths at all?
If we are talking about it specifically when it comes to things, such as meaning in life, there really aren't any truths, at least not an objective one. Of course, there are certain things that are hard to, if not impossible to argue against, but there are also a lot of things that don't have any objective truths to them. For example, views of bodily autonomy and the degree to which they should extend are very subjective. Morality can be very subjective and views on it can change a lot from person to person. The truths you are referring to in your post seem to not be in regards to something, such as physics or math, but rather seem to be based more on general things regards beliefs about life. Of course, that's just how I interpreted it, so maybe I interpreted it wrong.
However, your statement about being inside of a house also could still be applied to the whole "truths are based on perception" stuff I'm talking about. Let's say that you have two people (person A and person B). Person A claims that they are both sitting inside a room while Person B claims that they are sitting outside. Both disagree with each other and claim that the other is wrong and there must be something wrong with the other person, such as hallucination. Because of the fact that they both perceive their environment in two very different ways and there is no one else around they can ask for a third opinion, who is right? Who is the one in this situation who truly sees the truth? The point is, that our reality comes down to our perception. The way in which we perceive the world around us actually isn't one-to-one with reality because perception evolved to only be about as good as needed in order to allow for our ancestors to survive.
This is why we have to be so careful when it comes to research, replicating studies, taking note of potential design flaws, making sure to specify when something is a correlation vs a causation, using double-blind experiments, etc. Even then, there are cases of the consensus of truths amongst researchers changing because somebody decided to challenge them or because of changes to wider societal values allowing us to consider or accept things that we never accepted before. Researchers still have a hard time even agreeing on clear definitions for things. For example, defining what an emotion is can be challenging. We have some agreed upon aspects of them, such as them being a physiological reaction to stimuli and behavioural response components, but no consensus on how to define the term
emotion. What we consider to be the "truth" is generally something that can something end up being shaped more by our subjective interpretations of reality rather than being shaped by actual reality itself. Hence why things like the scientific method exist because understanding the world around us requires that we have to have a bunch of stuff in place in order to get past our own personal perceptions of reality and truly understand the world around us. Even then, it's still a struggle and our biases can still impact how we interpret things, like the results from studies.
I guess it's better to view it more like there are no "truths" on a more individual or philosophical level. We tend to interpret our views and opinions as objective facts, even though they aren't. On some level, truths do exist, but in the context of your post (which I interpreted as being more in line with things, like discussions on RTD, opinions on wider society, views on life, and whether or not there is a meaning to it, etc), there aren't really any "truths".