I would like to convert 23andme text file to NextGen to BAM file for Yfull.com to read. It is difficult to get answers on how to convert to SAM/BAM file for the 23andme text file to be converted to SAM/BAM tools
Having done 23andme myself I can tell you that your variant file, which contains SNP genotypes, cannot be converted to a bam file. It does not contain the same information as a bam file. It may be helpful to familiarize yourself with those filetypes and the technologies used to obtain them. A SAM/BAM file contains alignments of reads obtained by sequencing. Your standard* 23andme analysis doesn't have reads, as it uses a SNP array for determining the alleles at predefined positions. Markers which are not included in your 23andme file cannot be added by other means because those were not genotyped by the array. Therefore also Y-DNA cannot use your 23andme file or add additional markers.
*For the sake of completeness: I am aware that under rare circumstances 23andme can perform WGS for additional variant typing, but I do not assume this is the case for OP.
If you just want to get the markers which were not reported/genotyped by 23andMe (as you mentioned in the comment), you don´t want to convert your 23andMe data to SAM/BAM (which is most probably really difficult or impossible, as explained by @Wouter De Coster), but rather to perform imputation on your data file. This will give you a genotype file with genotype or allele probabilities for all the markers. While it will not give you a 100% certainty for the lacking variants, it can certainly give you more information on many of them.
NB: you can imputate the Y-chromosome variants only if your 23andMe file contain data from Y-chromosome. If you want to know about that option, let me know.
I think the closest approximation for a SNP chip would be the intensity values. When I asked 23andMe about obtaining these, the answer was that they don't plan on adding this feature.
Some programs use the .vcf file format instead of the 23andMe format, but I think the 23andMe format is compatible with relatively more 3rd party software than some other vendors. If I remember correctly, I think DNA.land even has an intermediate .vcf file, which you can download.
I actually think it is important that 23andMe doesn't impute the variants in your genotype table. However, if you are trying to dig deeper into some SNP chip data, I believe you can still get genotyping for free from Genes for Good. They provide a few different "raw data" formats (such as .vcf files, with and without imputation, as well as a "23andMe format" file) and I got the impression that they would consider providing an even more raw form of data (to test the effect of generating genotypes on your own, even thought I don't think most sites will change). However, to be clear, they also do not currently provide intensity values (or some other even more raw form of data).